Pressure-responsive switch



A 6 Hi 1. 8 04 May 5, 1942- E. w. F. HANKE PRESSURE-RESPONSIVE SWITCHFiled July 30, 1941 2 Sheets-5heet l \HHHHHHH lNVENTQR ATTORNEY y 1942-E. w. F. 'HANKE 2,281,764

PRESSURE-RESPONSIVE SWITCH Filed July 30, 1941 2 Sheets-Sheet 2 FIG. 4.

\NVENTOR ATTORNEY UNITED STATES I ATENT OFFICE PRESSURE-RESPONSIVESWITCH Edwin W. F. Hanke, Whitefish ay, Wis., assignor to Allen-BradleyCompany,

waukee, yVla, a

corporation of Wisconsin Application July 30, 1-941, Serial No. 404,629

5 Claims.

This invention relates to electrical switches of the type which respondto alter an electrical circuit when forces of predetermined intensityare caused to act thereon through a fluid-pressure device or othereffective instrumentality. The invention more specifically resides in anovel arrangement and formation of parts in such a switch, whicharrangement employs as the calibrated counterloading element a leafspring, the ends of which are restrained. In this apparatus theactuating force is applied between the ends of the calibrated spring tocause the central portion thereof to be deflected and such deflection iscommunicated to an over-center snap action device for controllingelectrical circuit elements.

Among the advantages of the above novel arrangementare the ease withwhich 'a strip or leaf spring having a definite calibration can beformed and the ease with which the ends of such a spring can beadjustably mounted for variation of the response of the switch. Anotheradvantage is the very flat, compact space occupied by the calibratedcounterloading elements of the apparatus.

Another advantage is the simplicity of the construction and the smallnumber of parts required. All of these advantages contribute toward theaccomplishment of a major object of this invention which is to provide areliable and accurate switch at a substantial saving in cost as comparedwith pressure switches heretofore known and used.

The apparatus of this invention is hereinafter more praticularlydescribed by reference to the accompanying drawings forming a parthereof. In the drawings there is set forth by way of illustration andnot of limitation one particular form of the apparatus of thisinvention. The several figures of the drawings are briefly described asfollows:

Fig. 1 is a side elevation, in section, of a pressure switch constructedin accordance with this invention:

Fig. 2 is a fragmentary plan view, in section, viewed through the planeindicated in Fig. 1 by the line 22, showing in greater detail thecounterloading spring and its mounting;

Fig. 3 is a detail view, in perspective, of the Fig. 5 is a detailsectional elevation of the overcenter switch parts in position oppositeto that shown for the same parts in Fig. 1; and

Fig. 6 is a detail view, in perspective, of the lower side of thecounterloading spring and its mounting.

More particularly described, the apparatus of this invention, asdepicted in the drawings, is mounted upon and partially housed by aframe I. The frame I is formed from heavy sheet metal by bendingupwardly from the horizontal base portion 2 thereof two similarverticallystanding side walls 3, only one of which appears in thedrawings. A circular indentation 4 formed in the material of the base ispositioned as shown in Fig. l to accommodate a pressurefoot 5. Securedto and projecting upwardly from the foot 5 is an actuator 6, whichpasses through an aperture in the indentation has shown.

Against the lower exterior face of the base 2, a flexible rubberdiaphragm l is securely clamped in place in position to cooperate withthe pressure-foot 5. Clamping is accomplished by means ofpressure-chamber 8 and screws 9 which engage tapped openings in the base2. Integrally formed with the pressure chamber 8 is a tapped boss to forattachment to the fluid-pressure system to which the switch is intendedto respond.

As a counterloading means for balancing the pressure in chamber 8, aresilient strip or leafspring H is provided. Spring II is composed ofthin resilient stock, such as clock-spring steel or the like, and is ofnearly rectangular shape except for a pair of ears I2 which project fromone end. The spring II is restrained against endwise and sidewisedisplacement by a bracket l3. which is secured by the rivet lugs l5 tothe base 2 as shown in Fig. 1. As appears more clearly in Fig. 6,endwise displacement is restricted by reason of the fact that spring IIhas an effective length close to, but slightly less than, the distancebetween the downwardly extending portions of the bracket l3. Sidewisedisplacement, on the other hand, is restricted by engagement of the earsl2 with sockets or openings in the right-hand vertical portion ofbracket [3 and by the rectangular configuration of the spring H. Thespring H is further held against lateral displacement by the nose IE onthe upper end of the actuator 6, said nose passing through a perforationin the spring I I provided for that purpose.

In' order to restrain the spring ll against transverse movement onopposite sides of the point of engagement of the actuator 6 therewith,

and a horizontally adjustable stop II. The

vertical adjusting screw passes through a tapped -opening in the top ofthe bracket [2 and is positioned so that its lower end engages thelefthand end of spring II in order that the transverse position at whichthe spring Ii is held may be regulated as desired. The stop II. on theother hand, is of the form shown clearly in Fig. 3, where it appearsthat it is provided with a tapped opening 20 and a small verticalprojection is above the tapped opening.

The top of bracket l3, near the right-hand end, is provided with a slot2| so dimensioned as to receive the projection it of the stop II. Inaddition, the vertical portion of the bracket It, at

,the right-hand end, is notched to receive the head of a horizontalcaptive screw 22, the threaded portion of which is in engagement withthe tapped opening 20 of the stop it. By reason of this construction,regulation of screw 22 permits the positioning of the horizontallyadjustable stop i8 at any horizontal position within its range ofmovement.

The vertical adjusting screw l1 and the horizontal stop It cooperate toresist the transverse thrust which the actuator switch applies to thespring ii when fluid-pressure acts upon the diaphragm i. r o

By reason of the lateral clearance between the spring I l and thebracket i3, no appreciable friction is involved in transversedisplacement of the spring II by the actuator 8. There is thus obtainedreliable and consistent counterloading by means of the spring ll,because the elastic properties of the spring II are the primary factorin determining the strength of the counterloading; Because of theextreme simplicity of the shape of the spring H and because of the readyavailability of material of good quality from which the spring is made,such a spring having the desired initial calibration can be veryeconomically formed. While it is preferable to employ a spring which isflat in its unstressed state, since such a spring is more easilyconstructed, a slight bowing of the spring in unstressed condition isnot objectionable.

Mounted upon the bracket it by means of mounting screws 23, 23 is aninsulating support 24 to which the over-center switch parts are secured.These parts comprise a thin resilient metallic-strip 26 of somewhatelongated shape, within which there is lengthwise disposed an elongatedU-shaped aperture 28 which serves to form the tongue 21. Between thepointed end of the tongue 21 and a pointed projection 28 formed atthebase of the U-shaped aperture 26 a small compression spring 28 isinterposed. The ends of the spring 29 are provided with indented cups,as shown, to facilitate engagement with the projection of tongue 2! andwith the projection 28.

By reason of the cooperation between spring 29 and member 25, spacedforward and return over-center positions are exhibited by these parts.The member 25 is securely anchored at its lefthand and by means ofrivets 30, 80 and the motion-limiting stop II. The stop Ii, also servesas a mounting for electric terminal screw 32. Upon the right-hand end ofmember 25 there is carried a pair of electrical contact buttons 88 whichare arranged to act between stationary contacts 34 and 38. As shown inFig. l, the movable contact buttons 23 are in electrical engagement withstationary contact 84. In this p sition the diaphragm I is relaxed andthe transverse displacement of spring Ii is at a minimum. In thisposition the thruster 3B bears with little or no pressure against thetongue 21 of the overcenter switch.

In Fig. 5 the over-center switch parts are shown in the position assumedwhen suflicient pressure is applied in chamber 8 to displace thediaphragm I and to transversely deflect the central portions of thespring ll. When this occurs the thruster I8 is caused to act upon thetongue 21, moving .the same until the over-center parts snap to theposition shown in Fig. 5.

Because of the spacing of the over-center positions of the switch parts25 and 29, the pressure switch above described is of the differentialtype, that is to say, the pressure at which the switch responds whilepressure is increasing differs from the pressure at which the switchresponds when pressure is decreasing. Therefore, by adjustment of thevertical adjusting screw 11 the level at which the differential occursmay be regulated within limits as desired without substantial alterationof the amount of the diiierential. However, if it is desired to alterthe magnitude of the differential, this may be accomplished byadjustment of the horizontally adjustable stop l8. In general, thecloser the horizontal stop it to the actuator 6 the greater will be theamount of the differential for any given setting of the verticaladjusting screw ll. of course the level at which the differential occursis also altered to some extent by adjustment of the horizontal stop I8.However, by selecting the proper position of adjustment for the verticaladjusting screw l1 and the horizontal stop it, both the level and theamount of the differential may be adjusted as desired, within limits. Ofcourse, if regulation of the amount of the differential is not desired,the horizontal stop l8 need not be moved, or may be omitted, or formedas a nonadjustable part of the apparatus. It is also apparent that thespring H may be formed of a single leaf, as shown, or may be oflaminated construction, employing several superimposed leaves, if a moreintense counterloading action is desired. 7

It will be apparent from the above description that the apparatus ofthis invention provides -a very simple and economically constructedcounterloading means and one which occupies a 'rela-' tively smallvertical height, thu facilitating a very compact structure for a switchof this charquate size and the provision of ample wiring terloadingmeans in the form of a leaf spring, a

base, mounting means associated with said base for preventing endwiseand sidewise displace ment of said spring and for retaining spacedportions of said spring against transverse movement,

- a pressures-responsive actuator mounted on said base and positioned toact transversely upon said spring between said transverse retainingmeans to deflect said spring transversely therebetween, and anover-center switch in cooperative engage- 75 ment with the transverselydeflectable portion of said spring adapted to be actuated by transversedeflection thereof, I

2. In a, pressure-responsive electrical switch,

the combination comprising a calibrated counthe combination comprising acalibrated'coun terloading means in the form of a thin strip oiresilient material, a base, mounting means assoterloading means in theform or a leaf spring, a 5

said mounting means including adjustable means for adjusting thetransverse position at which one portion of said spring is retained, apressureresponsive actuator mounted on said base and positioned to acttransversely upon said spring between said transverse retaining means todeflect said spring transversely therebetween, and an over-center switchin cooperative engagement with the transversely deflectable portion oraid spring adapted to be actuated. by transverse deflection thereof.

3. In a pressure-responsive electrical switch, the combinationcomprising a calibrated counterloading means in the form of a leafspring, a base, mounting means associated with said base ciated withsaid base comprising loose socket means for engagement with one end ofsaid strip and retaining means for preventing removal oi said end fromsaid socket, a pair of slops engaging spaced portions of the uppersurface of said strip for preventing transverse movement of saidportions, a pressure-responsive actuator mounted on said base andpositioned to act transversely upon said spring between said stops todeflect said spring transversely therebetween, and an 'over-centerswitch in cooperative engagement with the transversely deflectableportion of said spring adapted to be actuated by transverse deflectionthereof. 1

5. In a pressure-responsive electrical switch, the combinationcomprising a calibrated coun- 0 terloading means in the form or a thinstrip of for preventing endwise and sidewise displacestrip forpreventing endwise and sidewise disment or said spring and for retainingspaced portions of said spring against transverse movement, saidmounting means including adjustable means for adjusting the transverseposition at which one or said spaced portions of said spring istransversely retained, additional adjustable means for adjusting theendwise position at which the other of said spaced portions istransverselyretained, a pressure-responsive actuator mounted on saidbase and positioned to act transversely upon said spring between saidtransverse retaining means to deflect said spring transverselytherebetween, and an over-center switch in cooperative engagement withthe trans- .verselydeflectable portion of said spring adapted to beactuated by transverse deflection thereof.

4. In a pressure-responsive electrical switch,

0 spring adapted resilient material, a base,- mounting means associatedwith said base comprising a vertically projecting loose socket. meansfor engagement with one end of said resilient strip and a vertically vprojecting retainer adjacent the other end of said placement or saidstrip, a vertical adjusting screw in adjustable engagement with the topof one end of said strip, a horizontally adjustable stop in engagementwith the upper surface of the portion of said strip opposite the endthereof engaged by said vertical adjusting screw, a pressure-responsiveactuator mounted on said base and positioned to act transversely uponsaid strip to transversely deflect the same between said i verticaladjusting scre'w and the zone of adjustment of said horizontallyadjustable stop, and an over-center switch in cooperative engagementwith the transversely deflectable portion of said to be actuated bytransverse deflection thereof.

EDWIN W. F. HANKE.

